The present invention relates to the art of computer backup and safety systems. It finds particular application in conjunction with computerized banking in which a single central set of customer data files are accessed by a plurality of processor systems and will be described with particular reference thereto. However, it is to be appreciated, that the present invention is applicable to other computer systems and methods, particularly those in which large numbers of transactions are entered through a plurality of processors to update or modify a common set of files or data base systems.
Heretofore, information was stored in one or more computer files. Originally, a single computer or processor accessed the files to enter, withdraw, or modify the stored data. To protect the information stored in the files from system failures, errors, malicious tampering, machine failure, and the like, back-up copies of the data were made on a regular basis. Further in on-line systems, a record was commonly made of each transaction. In this manner, the status of the information stored in the files at any point in time could be recreated. Commonly, the processor included a journal file which kept a journal or backup copy of each of the transactions, i.e. operations which modified, entered, or deleted data from the files. More specifically, the processor commonly extracted information from the files, modified it during the transaction, and returned the modified or new data to the files. The journal record commonly included at least two of the data as retrieved from the files, the transaction, and the data which was returned to the files. In this manner, the journal provided a record of all transactions which was available for reconstructing the files, the sequence of transactions, and the like.
As the size of the computing systems grew and the number of transactions increased, it became impractical to access the files with a single computer. Accordingly, systems were developed for enabling a plurality of computers to access or share a single set of data files. A journal record of all transactions was still maintained. Because the same record could be modified several times, each time by a different one of the computers, it was necessary for the journal file to keep a record of the transactions in order. To this end, a journal processor or computer was interconnected with the shared files and with the plurality of computers or processors to monitor every transaction. The journal processor maintained a journal file in which the status of each record was recorded before and after each transaction. See for example Japanese patent application number 85 554/1984 to Nomiyama, laid opened May 17, 1984.
One of the problems with this prior art system resided in the cost and complexity of the journal processor. In order to interact with and record the transactions from a plurality of large processors or computers, a large, high speed, computer was required for the journal processor. The journal processor contributed not only to the cost of the system, but also to the complexity.
The present invention contemplates a new and improved computer system which enables a plurality of data processors to access shared data resources.